JPH0623853A - Thermal welding method - Google Patents

Abstract

PURPOSE:To omit a flash removing process and to reduce cost by cutting off the expanded part on the outer peripheral surface side of a material by the blade part of a welding device and the opposed part of an opposed device. CONSTITUTION:The leading end 201 of the rod material 20 grasped by a welding device 1 is preliminarily held to predetermined temp. in a heating process and allowed to collide with a heating plate 3 becoming a heat source and held to a contact state for a predetermined time to be heated. The deformed part 24 formed by the compression due to the collision with the heating plate 4 of the leading end 201 of the rod material 20 is escaped to an escape part 14 at the time of deformation. The rod material 20 is not scraped out by the edge 131 of a blade part 13 in such a state that the deformed part 24 is received in the escape part 14 at the time of deformation and the leading end 201 is heated and melted by the heat conduction from the heating plate 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fusion method used for fusing and unifying the tips of a plastic material and a mating member thereof.

[0002]

2. Description of the Related Art In a conventional heat fusion method, as shown in FIGS. 13 to 17, as a plastic material, for example, a tip 501 of a bar 50 and a mating member 51 made of plastic.
It is used when the product 5 integrated by fusing the tip 511 of the above is obtained. In this conventional heat fusion method, for example, a clamping step, a heating step, and a fusion step are sequentially performed. That is, in the clamping step, the fusing tool 6 is used, and the tip 501 to be fused of the rod 50 is slightly moved to the tip 6.
1 is grasped by the clamp portion 60 in a state of protruding (see FIGS. 13 and 14), and the opposing tool 8 is used to slightly tip the distal end 511 of the other plastic mating member 51 to be fused. Clamping part 80 with protruding
It is gripped by (see FIG. 14).

In the heating step, the tip 501 of the bar member 50 held by the clamp portion 60 is brought into contact with the heating plate 7 to heat and melt it (see FIG. 15). In the fusing step, the tip 511 of the mating member 51 and the tip 501 of the rod 50 melted in the heating step are brought into contact with each other, and the fusing tool 6 and the counter tool 8 are brought close to each other so as to further push them (see FIG. 16). .

Then, the tip 511 of the mating member 51 and the bar 5
The product 5 that is fused with the tip 501 of 0 and is integrated by the fused portion 52 is obtained (see FIG. 17).

[0005]

(1) The product 5 obtained by the conventional heat fusion method is
As shown in FIG. 17, on the outer peripheral surface 53 side, a bulging portion (burr) 520 in which a part of the fusion-bonded portion 52 bulges remains. The bulging portion (burr) 520 deteriorates the appearance of the product 5 and the accuracy. In addition, when the product 5 is required to have an appearance quality, it is necessary to remove the bulged portion (burr) 520 by further finishing after the above steps. Therefore, the number of processing steps is increased and the cost cannot be reduced. (2) Then, as shown in FIG. 19, when the tip end 511 of the mating member 51 and the tip end 501 of the bar material 50 melted in the heating step are brought into contact with each other and fused (FIG. 20).
), The bulging portion (burr) 520 bulging toward the outer peripheral surface 53 side of the product 5 is clamped and pressed by the blade portion 91 of the fusing tool 9 and the facing portion 80 of the facing tool 8 (see FIG. 21). Can be considered.

However, in this case, when the tip 501 of the bar 50 is brought into contact with the heating plate 7 for heating in the heating step prior to the fusion step, when the tip 501 collides with the heating plate 7 and the contact pressure increases. , The rod 50 has the tip 501 and the blade 9
It is compressed by collision with the first blade edge 911 and deforms toward the outer peripheral side to form a deformed portion 54 (see FIG. 18).

Then, the deformed portion 54 is scooped by the cutting edge 911 to generate a defective portion 55 (see FIG. 19). Therefore, in the product 5 obtained after finishing the fusion step following the heating step, the ring groove 56 having a substantially V-shaped cross section is formed on the outer peripheral side of the fusion portion 52 (see FIG. 22). Therefore, the external shape of the product 5 is deteriorated. An object of the present invention is to provide a heat fusion method that solves the problems (1) and (2).

[0008]

The heat fusion method of the present invention comprises:
A clamp part for holding a plastic material having a predetermined cross-sectional shape, and a deforming escape part that is integrally formed at the tip of the clamp part and escapes the deformed part of the bar deformed when it collides with the heating plate. Using a fusing tool having an inner peripheral shape that is larger than the outer peripheral surface shape and having a blade portion whose tip is a blade shape, the clamp portion with the tip of the material to be fused slightly protruding to the tip of the blade portion. Clamping step of gripping the other mating member made of plastic to be fused together with the above, and the tip of the gripped material is made to collide with the heating plate to be heated and melted, and deformed by the collision. A heating step of allowing the deformed portion of the material to escape to the escape portion at the time of deformation, a facing tool having a facing part facing the blade of the fusing tool, and abutting the mating member and the tip of the melted material, and The fusion to push forward And the facing member is brought close to each other, and a bulging portion that bulges toward the outer peripheral surface side of the material by being pushed forward is heat-sealed by pressing the blade portion of the fusion member and the facing portion of the facing device. And a fusion step.

The material and the mating member used in this heat fusion method are made of plastic and have the same sectional shape. The cross-sectional shape may be circular, quadrangular, rectangular, or any other shape. Further, the material and the mating member may be cylindrical. This fusing tool and facing tool are used when fusing the two materials and the mating member at each tip to integrate them into one, or when fusing both tips of one material to form a loop. Can be used for.

The fusing device has a blade portion at the tip of the clamp portion and a relief portion at the time of deformation formed on the inner peripheral side of the blade portion. The blade has a ring-shaped blade tip. The inner peripheral shape of the cutting edge viewed from the front side is larger than the outer peripheral shapes of the material and the mating member by the relief portion at the time of deformation.

The blade portion presses the bulging portion, which bulges toward the outer peripheral surface side of the material at the time of fusing the both ends of the material and the mating member, together with the facing portion of the facing tool and pushes it out. The deformation relief portion is a ring-shaped space formed in a predetermined depth direction from the blade tip of the blade portion and formed between the inner peripheral surface of the blade portion and the outer peripheral surface of the grasped material. The size of the escape portion at the time of deformation, that is, the width of the gap between the inner peripheral surface of the blade and the outer peripheral surface of the material and the distance in the depth direction from the cutting edge of the blade correspond to the size of deformation of the material. Various settings can be made.

The deforming escape portion escapes the deformed portion of the material which is deformed by the contact when the tip of the material collides with the heating plate to heat the material in the heating step. As a result, the deformed portion does not come into contact with the blade edge of the blade portion and is not scooped out. The collision is a high pressure at which the material is pressure-deformed between the tip and the portion gripped by the clamp portion of the fusion tool when the tip of the material is heated by contacting the heating plate for a predetermined time in the heating step. Refers to the state of contact.

The facing member has a facing portion facing the blade portion of the fusing tool at the tip of the clamp portion for holding the mating member.
The facing portion may be a flat vertical surface, the same as the fusing tool may be used as the facing tool, and the blade portion may be used as the facing section. That is, when a fusing tool having a blade is used as the facing tool, the two fusing tools are in a use state in which the fusing parts are arranged at positions where the blades face each other. Then, in the fusion step, the bulging portion that bulges toward the outer peripheral surface side of the material from the fusion bonding portion can be sandwiched and pushed by two blade portions facing each other.

[0014]

According to the heat fusion method of the present invention, the clamping step, the heating step and the fusion step are sequentially carried out. It should be noted that prior to the execution of each step, a fusing tool and a facing tool, a plastic material having a predetermined cross-sectional shape to be fused and a mating member are prepared.

The fusing tool serves as a relief portion during deformation for releasing a deformed portion of the rod member which is integrally formed at the tip of the clamp portion and deformed when the rod collides with the heating plate. It has a blade part with an inner peripheral surface shape larger than the outer peripheral surface shape and the tip of which is a blade shape. Further, the facing tool has a clamp part for gripping a mating member, and a facing part facing the blade part of the fusing tool at the tip of the clamp part. (1) In the clamping step, the fusing tool is used to hold the tip of the plastic material to be fused with the clamping part while slightly projecting to the tip of the blade part, and the fusing tool is used to The other plastic mating member to be attached is grasped by the clamp portion in a state in which the tip thereof slightly projects to the tip of the facing portion. (2) In the heating step, the tip of the material gripped by the fusing device is caused to collide with a heating plate which is held at a predetermined temperature in advance to heat and melt it. Along with this collision, the material is deformed between the part gripped by the clamp part and the tip to become a deformed part. This deformed portion escapes to the escape portion during deformation and does not bulge outside from the blade tip of the blade portion. (3) In the fusion step, the mating member and the tip of the material melted in the heating step are brought into contact with each other, and the fusion tool and the opposing tool are brought close to each other so as to further push the material.

Then, the mating member and the tip of the material are fused,
A part of the fused material bulges toward the outer peripheral surface of the material. The bulging portion is pressed by the blade portion of the fusing tool and the facing portion of the facing tool, and is completely pressed. Therefore, according to the heat fusion method of the present invention, when the tip of the material is heated by colliding with the heating plate in the heating step,
The deformed portion of the material is released to the escape portion during deformation.

Therefore, it is possible to prevent the deformed portion from being scooped by the cutting edge. Further, in the fusing step, two actions are performed, that is, the action of fusing the tip of the raw material and the tip of the mating member and the action of pushing out and removing the bulging portion (burr) formed by the fusing.

[0018]

【Example】

(Example 1) A thermal fusion bonding method of Example 1 will be described with reference to FIGS. In addition, as a target member to be fused by the heat fusion method, a rod member 20 (see FIGS. 2 and 3) as a plastic material having a circular cross section, and another member to be fused to the rod member 20. As a member, a rod 21 (see FIG. 4) as a plastic material having a circular cross section is used, and a rod-shaped product 2 (see FIG. 8) in which the rods 20 and 21 are fused and integrated is obtained. Is.

First, the fusing tool 1 and the facing tool 3 used in the thermal fusing method of the first embodiment will be described. The fusing tool 1 is shown in FIGS.
As shown in FIG. 2, it is composed of a pair of metal clamp parts 10 and 10 that can be divided into two and can be integrally connected.
The overall shape is a cube. A device (not shown) is used for the fusion bonding tool 1 in order to integrally connect and hold the clamp portions 10 and 10, or to release the connected and held state and to divide into two.

The clamp portions 10 and 10 are semi-circular hole portions 120 and 120 forming holding holes 12 through which the rod 20 is inserted and held, and semi-circular hole portions 120 and 120 integrally formed on the tip 11 side, on the opposite sides in a symmetrical shape. The blade 13 has a blade portion 13 and a relief relief portion 14 formed on the inner peripheral side of the blade portion 13. Holding hole 12 formed by the semi-circular hole portions 120, 120
Has the same circular cross section as the outer peripheral surface 200 of the bar 20.

The blade portion 13 is, as shown in FIGS.
The bar member 2 is formed integrally with the tip 11 of the clamp portion 10
0 has an inner peripheral surface 130 that is larger than the outer peripheral surface 200 by the escape portion 14 at the time of deformation, and has a ring-shaped cutting edge 131 at the tip.
Is formed. The cross-sectional shape of the blade portion 13 is a substantially triangular shape having the apex of the ring-shaped blade 131, and the inner peripheral diameter R _{3 is} larger than the inner peripheral diameter R ₂ of the inner peripheral surface 120 of the holding hole 12 by a predetermined dimension.
The inner peripheral surface 130 is inclined about 30 ° outward, and the tip has a sharp shape.

The deforming relief portion 14 is provided at the tip 2 of the bar member 20.
01 escapes the deformed portion 24 generated when the heating plate 4 collides with the heating plate 4, and the inner peripheral surface 130 of the blade portion 13 and the clamp portion 1
It is a space area (clearance) formed between the outer peripheral surface 200 of the bar member 20 held at 0 and inserted into the holding hole 12. Therefore t (interval width in the radial direction) radial size of the deformation during the relief portion 14, the value of the outside diameter R ₁ of the inner circumference R ₂ and material 20 for holding hole 12, the inner peripheral diameter R ₂ and It is relatively determined by the value of the inner peripheral diameter R ₃ which is larger than the outer peripheral diameter R ₁ .

In the first embodiment, the radial size t of the relief portion 14 at the time of deformation is set to 0.2 mm. Also,
The dimension L (the interval length in the direction extending along the axis P) L from the cutting edge 131 is set to 3 mm. Opponent 3
Is made up of a pair of metal clamp portions 30 and 30 that can be divided into two and integrally connected, and has an overall cubic shape (see FIGS. 4 and 6). The two clamp parts 30, 30 have semi-circular hole parts 320, 320 forming a holding hole 32 through which the bar 21 is inserted and gripped, on the sides facing each other in a symmetrical shape.

Further, the clamp portions 30, 30 have an opposed portion 31 having a flat vertical surface on the front end side opposed to the blade portion 13 of the fusion bonding tool 1. In this way, each clamp part 30, 30
Is the blade portion 13 and the deformation relief portion 14 of the fusion bonding tool 1.
Other than this, the clamp part 1 has no
Same as 0 and 10.

The fusion tool 1 and the facing tool 3 are held by a device (not shown) so that they can move close to each other on the same axis P while gripping the rods 20 and 21, respectively. . Then, the clamp step, the heating step, and the fusion step of the heat fusion method of Example 1 are sequentially performed. That is, in the (1) clamping step, the tip 201 to be fused is slightly protruded from the blade tip 131 of the blade 13 with respect to the bar 20 by the two clamps 10 and 10 of the fusion tool 1. While gripping (see FIGS. 2 and 3), the tip portion 211 is slightly gripped by the clamp portions 30, 30 of the facing tool 3 so as to be fused to the bar material 21 (see FIG. 4). ). (2) In the heating step, the tip 201 of the bar member 20 gripped by the fusing tool 1 is kept in contact with the heating plate 4 which is previously held at a predetermined temperature and serves as a heat source, for a predetermined time. The saucer is heated (see FIG. 5). At this time, the tip 20 of the bar 20
1, the deformed portion 24 generated by the compression accompanying the collision with the heating plate 4 escapes to the escape portion 14 during deformation. Then bar 2
In the state of 0, the deformed portion 24 is accommodated in the escape portion 14 at the time of deformation, and is not scooped by the cutting edge 131 of the blade portion 13, and the tip 201 is heated and melted by heat conduction from the heating plate 4. (3) In the fusion process, the bar material 20 melted in the heating process
The tip 201 of the rod and the tip 211 of the bar 21 are brought into contact with each other (see FIG. 6).

In this state, the fusing tool 1 and the counter tool 3 are brought closer to each other so as to further push the both ends 201 and 211. Then, the melted tip 201 of the bar 20 and the bar 21
And a tip end 211 of each of them are fused and integrated at a fused portion (hatched portion) 22. Along with this, a part of the fused portion 22 bulges toward the outer peripheral surface 23 side of the product 2 to form a bulged portion (burr) 220.

Here, according to the first embodiment, since the fusing tool 1 and the facing tool 3 are pushed toward each other in the proximity direction, the bulging portion 220 has the cutting edge 131 of the blade portion 13 of the fusing tool 1.
And the facing portion 31 of the facing tool 3 is pressed and pushed (see FIG. 7). As described above, according to the heat fusion method of the first embodiment, the tip portion 201 of the bar member 20 forms the deformed portion 23 generated by the compression accompanying the collision with the heating plate 4 in the heating step, and the blade portion 13 is formed.
The action of letting the deformation escape portion 133 escape and the pushing in the direction of bringing the fusion tool 1 and the opposing tool 3 closer to each other in the fusion process,
The melted tip 201 of the material 20 and the tip 21 of the material 21
The fusing action of fusing 1 with 1 and the bulging portion (burr) 220 generated by this fusing action are clamped between the blade portion 13 of the fusing tool 1 and the facing part 31 of the facing tool 3. Can be pushed down and pushed.

Therefore, according to the heat fusion method of the first embodiment, the product 2 (see FIG. 8) obtained by completing the steps of the clamping step, the heating step and the fusion step is the outer peripheral surface 23.
There is no ring-shaped groove formed in the cutting edge 131,
Further, a post-process (finishing process for removing burrs) which has been conventionally required is not required, and this post-process can be omitted, which is advantageous in terms of manufacturing cost.

(Embodiment 2) The heat fusion method of the second embodiment comprises a clamping step, a heating step, and a fusion step, and the above steps are sequentially carried out. In the heat fusion method of the second embodiment, the facing tool 3 facing the fusing tool 1 used in the first embodiment.
Instead of the above, two fusing tools 1 are used, and one of them is arranged at the same position as the facing tool 3 to form a facing tool 1A. That is, the fusing tool 1 and the facing tool 1A arranged to face the fusing tool 1 are the same.

Therefore, in the heat fusion method of the second embodiment, the blade portion 13 of the fusing tool 1 and the blade portion 13 of the facing tool 1A are arranged and used at positions opposed to each other, and other than the fusing step. Is
This is similar to the case of the first embodiment. Therefore, the second embodiment
In the heat fusion method of No. 1, the fusion process performed after the clamping process and the heating process are performed in the same manner as in Example 1 will be mainly described.

In the clamping step of the second embodiment, the fusing tool 1 and the facing tool 1A are used, and the respective clamp parts 10 and 1 are used.
0, the tip 2 to be fused to the rods 20 and 21.
01 and 211 are gripped in a state of slightly protruding from the blade edge 131 of the blade portion 13. Next, in the heating step, the tip end 201 of the bar member 20 and the tip end 211 of the bar member 21 allow the deformed portion 24 generated by the compression accompanying the collision with the heating plate 4 to escape to the escape portion 14 during deformation. Then, the bar 20 is deformed 2
In a state in which 3 is accommodated in the escape portion 133 during deformation, the tip 201 is not engraved by the cutting edge 131 of the blade portion 13, and the tip 201 is heated by heat conduction from the heating plate 4 and melts (see FIG. 9).

In the fusion process, the bar material 2 melted in the heating process
The tip 201 of 0 and the tip 211 of the bar 21 are brought into contact with each other (see FIG. 10). In this state, both tips 201, 21
The fusion tool 1 and the counter tool 1A are brought close to each other so that 1 is pushed forward. Then, the melted tip 201 of the rod 20 and the tip 211 of the rod 21 are fused and integrated at the fused portion (hatched portion) 22, and the fused portion 22 is provided on the outer peripheral surface 23 side. Part of the bulge and the bulge portion (burr) 220
Is formed.

At this time, according to the second embodiment, since the fusing tool 1 and the counter tool 1A are pushed toward each other,
The bulging portion 220 includes a blade edge 131 of the blade portion 13 of the fusing tool 1 and a blade edge 13 of the blade portion 13 of the facing tool 1A that face each other.
It is squeezed by 1 and pushed down (see FIG. 11). As described above, in the heat fusion method of the second embodiment, only the melted tip 201 of the rod 20 and the tip of the rod 21 are pushed in the direction of bringing the fusion tool 1 and the opposing tool 1A closer to each other in the fusion step. The fusing portion (burr) 220 generated by the fusing action for fusing and integrating with 211 and the bulging portion 220 generated by this fusing action
And the blade portion 13 of the facing tool 1A are pressed to push it out, whereby the product 2 shown in FIG. 12 is obtained.

Therefore, in the fusing step of the second embodiment, the bulging portion (burr) 220 formed is replaced with the bulging portion (burr).
With the two blade portions 13 and 13 facing each other through 220, the blade can be pushed all the way faster than in the case of the first embodiment.

[0035]

EFFECTS OF THE INVENTION According to the heat fusion method of the present invention, (1) in the heating step, when the tip of the material is collided with the heating plate and heated, the deformed portion of the material is released to the escape portion during deformation. Is done. Therefore, it is possible to prevent the deformed portion from being scooped by the cutting edge. Further, the product obtained after the heating process and the fusing process has a cross section of approximately V
The outer shape can be improved without forming the V-shaped ring-shaped groove. (2) In the fusing step, there are two actions: an action of fusing both ends of the plastic material and its counterpart member, and an action of pushing out and removing the bulged portion (burr) formed by the fusing. The action takes place.

Therefore, the product obtained after the fusion-bonding step does not have a substantially V-shaped ring-shaped groove formed on the outer peripheral surface thereof, and no bulging portion remains, so that the appearance and accuracy of the product appearance are improved. Further, the post-process (finishing process) for removing the bulging portion, which is required for the product obtained by the conventional heat-sealing method, becomes unnecessary, and the processing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing a fusing tool used in a thermal fusing method according to a first embodiment of the present invention in perspective.

FIG. 2 shows a clamping step in the thermal fusion bonding method according to the first embodiment of the present invention, and the fusion bonding tool of FIG. The perspective view which shows the rod material as a perspective view.

FIG. 3 is a side view showing a clamp portion and a rod material as a plastic material as viewed from the direction of arrow S in FIG.

FIG. 4 is a perspective view showing a facing member used in the heat-sealing method according to the first embodiment of the present invention, which is divided into two parts, and a pair of two clamp parts and a plastic counterpart member held by the clamp parts. Fig.

FIG. 5 is a side view showing a heating step in the heat fusion method of Example 1 of the present invention.

FIG. 6 is a side view showing a state in which a material and a mating member are in contact with each other in a fusion bonding process, as in FIG.

FIG. 7 is a side view showing a fusion state between a material and a mating member and a state in which burrs are cut and removed in the fusion process, as in FIG. 6;

FIG. 8 is a side view showing a product obtained by completing each step in the heat fusion method of Example 1 of the present invention.

FIG. 9 is a side view showing a heating step in the heat fusion method of Example 2 of the present invention.

FIG. 10 is a side view showing a contact state between a bar material as a raw material and a mating member in the fusion bonding process, similar to FIG. 9.

FIG. 11 is a side view showing a fusion state between a bar and a mating member and a state in which burrs are cut and removed in the fusion process, as in FIG. 10.

FIG. 12 is a side view showing a product obtained by completing each step in the heat fusion method of Example 2 of the present invention.

FIG. 13 is a perspective view showing in perspective a fusing tool used in a conventional heat fusion method.

FIG. 14 shows a clamping step in the conventional heat fusion method, and divides the fusing tool and the facing tool used in the conventional heat fusion method into two parts, one with a pair of a clamp part and a clamp part. FIG. 3 is a perspective view showing a bar member as a plastic material to be gripped and a mating member in perspective.

FIG. 15 is a side view showing a heating step in the conventional heat fusion method.

FIG. 16 is a side view showing a fusing step in the heat fusing method, similar to FIG.

FIG. 17 is a side view showing a product obtained by completing each step in the heat fusion method of the conventional example.

FIG. 18 is a side view showing a heating step in the heat fusion method of the comparative example.

FIG. 19 is a side view showing a contact state between a bar material as a raw material and a mating member in the fusion bonding process, similar to FIG.

FIG. 20 is a side view showing a fusion-bonded state of a bar and a mating member in the fusion-bonding step, similar to FIG.

FIG. 21 is a side view showing a state in which burrs are cut and removed in the fusion bonding step, similar to FIG.

FIG. 22 is a side view showing a product obtained by completing each step in the heat fusion method of the comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fusing tool 3, 1A ... Opposite tool 10 ... Clamp part 11 ... Tip 12 ... Holding hole, 120 ... Semicircular hole part 13 ... Blade part 131 ... Blade edge
31 ... Opposing part 14 ... Escape part at the time of deformation 2 ... Product after fusion 20 ... Bar material as plastic material 23 ... Deformation part 21 ... Plastic counterpart member 22 ... Fusion part 220 ... Swelling part (burr) )

Claims (1)

[Claims] 1. A clamp part for gripping a plastic material having a predetermined cross-sectional shape, and a deformed part of the bar which is integrally formed at the tip of the clamp part and is deformed when it collides with a heating plate. Part of the material, the inner peripheral shape of which is larger than the outer peripheral surface shape of the material, and a fusing tool having a blade part whose tip is a blade shape, and the tip to be fused of the material is slightly projected to the tip of the blade part. Clamping process in which the clamp part holds the other mating member made of plastic to be fusion-bonded in the state, and the tip of the grasped material collides with the heating plate to heat and melt it. A heating step of escaping the deformed portion of the material that has been deformed along with the escaping portion at the time of deformation, an opposing tool having an opposing part facing the blade portion of the fusing tool, and the tip of the material melted with the mating member. Abut and push further As described above, the fusion tool and the facing tool are brought close to each other, and the bulging portion that bulges to the outer peripheral surface side of the material by being pushed forward is completely cut off by the blade part of the fusion tool and the facing part of the facing tool. And a heat-sealing method, wherein the heat-sealing step comprises: